Process of manufacturing electrical contact members



1-2 ADAMs May 9, 19330 PROCESS OF MANUFACTURING ELECTRICAL CONTACTMEMBERS Filed Nov. 24, 1930 Patented May 9 1933 UNITED STATES PATENTOFFICE ARTHUR H. ADAMS, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, 011' NEW YORK, N. Y., A CORPORATION OF NEW YORKPROCESS OF MANUFACTURING ELECTRICAL CONTACT MEMBERS Application filedNovember 24, 1930. Serial No. 497,755.

This invention relates to a process of manufacturing electrical contactmembers, and more particularly to a process of manufacturing bimetallicelectrical contact elements.

It is the object of the present 1nvent1on'to provide a process ofmanufacturingbimetallic, electrical contact elements, utilizing aminimum quantity of contact metal wh1le providing a substantialeffective contact surface.

In accordance with one embodiment, the invention contemplates forming asubstantially rectangular ribbon of base metal, forming a strip ofcontact metal to a sub stantially elliptical cross-sectional shape withlaterally extending portions at the smaller ends of the ellipse, andwelding the contact metal to the base metal. After the strip of contactmetal and the ribbon of. base metal have been shaped as describedhereinbefore and welded together, the laterally extending portions ofthe contact metal are bent out of their normal plane to surroundpartially the adjacent edges of the base metal, thereby to provide agreater area protected by contact metal when the contact elements aremounted upon contact springs of electrical apparatus. A composite stripof base and contact metal formed as hereinbefore described may be cut topredetermined lengths and welded to contact springs and angularlydisposed with respect to each other.

A better understanding of the invention may be had by referring to thefollowing de'- tailed description of one embodiment thereof whenconsidered in conjunction with the accompanying drawing, wherein Fig. 1is a cross-sectional view through a forming apparatus in which the wireof contact metal is positioned and formed to the shape shown;

Fig. 2 is a sectional view through a strip of contact metal and ribbonof base metal'and a pair of welding electrodes showing the relativeposition of the electrodes and the base and contact metal before thewelding operation takes place;

Fig. 3 is a cross-sectional view of a com- 50 posite bimetallic stripcomposed of a ribbon of base metal and strip of contact metal after thewelding operation;

Fig. 4 is a plan view showing a composite bimetallic strip after thelaterally extending portions of the contact metal have been formed outof their normal plane;

Fig. 5 is a sectional view taken on the line 5-615 of Fig. 4 in thedirection of the arrows, an

Fig. 6 is a perspective View of a contact spring with the compositebimetallic contact element welded thereto.

Referring now to the drawing wherein like reference characters designatethe same parts throughout the several views, the numeral 7 indicates awire of contact metal such as platinum, palladium, alloys of platinumand gold or palladium and gold or sim ilar metals of the compositioncommonly used in electrical contact elements which has been deformedfrom a regular cylindrical w1re by means of cooperating swage blocks 8and 9 to the shape shown wherein portions of the metal of the wire havebeen swaged outwardly at diametrically opposite points to form laterallyextending projections 11 and 13 and upper and lower rounded surfaces 10and 12, respectively. After a wire of contact metal has been so formed astrip or ribbon of base metal 15 of nickel silver or pure nickel of asubstantially rectangular cross-section with rounded edges is combinedwith the contact metal in the manner shown in Fig. 2 with the roundedlower surface 12 of the contact metal making a line contact with thebase metal and welding electrodes 17 and 19 are applied to the lower,flat surface of the base metal 15 and the upper, rounded surface 10 ofthe wire 7 of contact metal and a welding current is applied to theelectrodes in any well known manner. As is usual in welding operations,pressure is exerted upon the contact and base metals while the weldingcurrent is being applied to cause them to join together by fusionthereof in the manner shown in Fig. 3.

It has been found that because of the difference in fusing temperaturesof contact metal such as platinum or palladium and alloys thereof andbase metal such asnickel silver, pure nickel or other metals havin ahigh resistance to corrosion, that if a line contact is rovided betweenthe two metals, as shown in Fig. 2, the welding current in assing fromthe wire 7 of platinum or Slmlar metal to the strip 15 of nickel silveror similar metal will be concentrated and will encounter the greatestresistance at the line of contact and the metals will fusesimultaneously roviding a very satisfactor weld with an al oy ofthetwo-metals being ormed in the area indicated by the numeral 18, Fig. 3.This substantially simultaneous fusing of the contact and base metals isdue to the fact that the base metal being large in crosssectional areawill not heat as rapidly as the contact metal, which at the line wherethe welding action takes place and where the concentration of thewelding current occurs is relatively small in cross-sectional area,thereby causing the base and contact metals along the line of contacttherebetween to reach their melting temperatures at approximately thesame time, thus providing an intimate mixture and alloying of the metalsand a strong welded union between them.

After a ribbon of base metal and a wire of contact metal have beenwelded together to form a continuous strip of theshape shown incross-section in Fig. 3, the laterally extending projections 11 and 13of contact metal are formed by suitable forming-members to the shapeshown in cross-section in Fig. 5, whereupon the composite strip soformed may. be cut to predetermined lengths along the lines 20 and 21(Fig. 4) to form composite bimetallic contact elements 23. The laterallyextending projections 11 and 13 thus form an apron over the base metalto provide a greater area covered with contact metal thereby preventingthe deposition of oxides of the base metal on the contact metal whichwould otherwise be caused by arcing between the base and contact metalof cooperating contact elements.

Contact elements 23 formed in accordance with the steps outlinedhereinbefore may then be secured by welding to springs 22 for use inelectromagnetic relays or like apparatus. It will be noted that thecontact element 23 as shown in Fig. 6, is angularly disposed upon thefiat surface of the contact spring 22. Another contact element 23 fixeddiagonally to a spring (not shown) will provide a cooperating contactingsurface for use in conjunction with the contact element and spring shownin Fig. 6, the contact elements being angularly disposed with respect toeach other, a cross contact being thus provided.

Although this invention has been described as utilizing a specific formof ribbon or base metal and wire of contact metal, it will be understoodthat various modifications and adaptations of the method outlined indetail hereinbefore may be made without departing from the scope of theinvention, which is to be limited only by the scope of the appendedclaims.

\Vhat is claimed is:

1. The process of manufacturing bimetallic contact elements whichincludes forming a base metal to predetermined dimensions, forming acontact metal to a predetermined irregular formation, combining the basemetal and contact metal, welding the contact metal to the base metal toform a composite member, and forming the contact metal over the basemetal to protect the base metal.

2. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of predetermined dimensions,pressing a wire of contact metal to form horizontally extendingprojections upon diametrically opposite portions thereof, combining theribbon of base metal and the wire of contact metal with the projectionsof the wire of contact metal parallel to the widest surface of the basemetal, welding the base metal and wire of contact metal while maintainedin that relative position, and thereafter forming the composite stripinto its final shape.

3. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of predetermined dimensions,pressing a wire of contact metal to form horizontally extendingprojections upon diametrically opposite portions thereof, combining theribbon of base metal and the wire of contact metal with the projectionsof the contact metal parallel to the widest surface of the base metal,welding the base metal and the wire of contact metal while maintained inthat relative position, and forming the projections of contact metal outof their normal horizontal plane to surround partially the verticalportions of the base metal.

4. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of predetermined dimensions,pressing a wire of contact metal to form horizontally extendingprojections upon diametrically opposite portions thereof, combining theribbon of base metal and the wire of contact metal with the projectionsof the contact metal parallel to the widest surface of the base metal,welding the base metal and the wire of contact metal while maintained inthat relative position, and formingthe projections of contact metal outof their normal horizontal plane to surround partially the verticalportions of the base metal while retaining the rounded upper surface ofthe contact metal.

5. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of predetermined dimensions,forming contact metal to a predetermined irregular formation, combiningthe neoaeso base metal and contact metal, welding the contact metal tothe base metal, forming the composite strip into its final shape, andweld ing the composite strip in its final shape to a contact spring.

6. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of substantially rectangularcross-section, forming a wire of contact metal to an approximatelyelliptical cross-sectional shape with projecting portions at the smallerends of the ellipse, welding the contact metal to the base metal withthe pro jecting portions of the contact metal parallel to the flatsurface of the base metal, and forming the, projecting portions of thecontact metal to surround partially the base metal,

7. The process of manufacturing bimetallic contact elements whichincludes forming a ribbon of base metal of substantially rectangularcross-section, forming a wire of contact metal to an approximatelyelliptical crosssectional shape with projecting portions at the smallerends of the ellipse, welding the contact metal to the base metal withthe projecting portions of the contact metal parallel to the fiatsurface of the base metal, forming the projecting portions of thecontact metal to surround partially the base metal, cutting thecomposite base and contact metal strip into predetermined lengths, andwelding the composite strip to contact springs.

8. The process of manufacturing bimetallic contact elements whichincludes forming a base metal of substantially rectangularcross-sectional shape, forming outwardly extending ridges on a wire ofcontact metal, combining the base metal and the contact metal, weldingthe contact metal to the base metal, and forming the ridges of thecontact metal over the base metal.

9. The process of forming bi-metallic con-= tact elements for contactarms which comprises forming a base member and a contact 7 member,providing one of said members with a convex surface to make a linecontact with the other to localize an electric current, applying anelectric current to the parts to weld them together into a. compositemember,

forming one of the members over the other member to enclose a portionthereof, and weldmg the composite member to a contact arm.

In witness whereof, I hereunto subscribe my name this 18th day ofNovember, A, D.

ARTHUR H. ADAMS,

